1. Field of the Invention
The invention relates to an exhaust gas control apparatus for an internal combustion engine. More particularly, the invention relates to an exhaust gas control apparatus for an internal combustion engine, which includes exhaust gas purification means that has oxidizing ability, and that is provided in an exhaust passage.
2. Description of the Related Art
International Application Published under the Patent Cooperation Treaty No. 01/073273 discloses a technology relating to an exhaust system of an internal combustion engine, in which a particulate filter (hereinafter, referred to as “filter”) for capturing particulate matter (hereinafter, referred to as “PM”) in exhaust gas is provided in an exhaust passage. In this technology, an exhaust throttle valve that is provided in the exhaust passage at a portion downstream of the filter is fully opened, and then is closed at given time intervals, whereby the PM with which the filter is clogged is removed.
Also, International Application Published under the Patent Cooperation Treaty No. 01/073271 discloses a technology relating to an exhaust system of an internal combustion engine, in which a filter is provided in an exhaust passage. In the technology, air is blown to a front end surface of the filter in a lateral direction of the front end surface of the filter, whereby PM deposited in the front end surface of the filter is blown off. Also, Japanese Patent Application Publication No. JP(A) 2003-206722 and Journal of Technical Disclosure published by Japanese Institute of Invention and Innovation No. 03-503795 disclose related art.
In an exhaust system of an internal combustion engine, in which exhaust gas purification means having an oxidizing function such as a filter supporting an oxidation catalyst or a NOx storage reduction catalyst is provided in an exhaust passage, PM discharged from the internal combustion engine adheres to the exhaust gas purification means, and is deposited in the exhaust gas purification means.
In such an internal combustion engine, a PM removal control is performed. By performing the PM removal control, for example, fuel is supplied into the exhaust passage at a portion upstream of the exhaust gas purification means so that unburned fuel components are supplied to the exhaust gas purification means, and a temperature of the exhaust gas purification means is increased using heat of oxidation of the unburned fuel components in the exhaust gas purification means, whereby the deposited PM is oxidized and removed.
However, a temperature is unlikely to increase in an upstream end surface of the exhaust gas purification means, which is in an upstream side of the exhaust gas purification means in a direction in which the exhaust gas flows. That is, the temperature is unlikely to increase in the front end surface of the exhaust gas purification means even when the PM removal control is performed. Therefore, it may be difficult to remove the PM deposited in the front end surface even by the PM removal control.
Also, in the PM removal control, when the unburned fuel components are supplied to the exhaust passage at a portion upstream of the exhaust gas purification means so that the unburned fuel components are supplied to the exhaust gas purification means, part of the supplied unburned fuel components may adhere to the front end surface of the exhaust gas purification means. If the unburned fuel components adhere to the front end surface of the exhaust gas purification means, the unburned fuel components adhering to the front end surface and the PM in the exhaust gas are mixed together. As a result, the PM may be more likely to be deposited in the front end surface of the exhaust gas purification means.
If an amount of the PM deposited in the front end surface of the exhaust gas purification means increases to an excessive value, a pressure in the exhaust passage at a portion upstream of the exhaust gas purification means may increase to an excessive value, which may influence an operating state of the internal combustion engine.